


Advantages

by Tillyalf427



Category: Free!
Genre: Alpha Matsuoka Rin, Alpha Yamazaki Sousuke, Alpha/Beta/Omega Dynamics, Anal Fingering, Anal Sex, Blow Jobs, Double Penetration, Fluff and Smut, Knotting, M/M, Mating Cycles/In Heat, Multi, Omega Shigino Kisumi, Oral Sex, Smut, Teasing
Language: English
Status: Completed
Published: 2021-02-13
Updated: 2021-02-13
Packaged: 2021-03-13 16:20:23
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,715
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29404692
Author URL: https://archiveofourown.org/users/Tillyalf427/pseuds/Tillyalf427
Summary: Having two alphas could be argued to be both a good and a bad thing. Kisumi had learnt this first hand quickly after reconnecting with Sousuke and Rin.He had already settled on a long list of advantages that came with having two mates, from the extra protection he got from creeps anytime they went out to his heats lasting half as long.
Relationships: Matsuoka Rin/Shigino Kisumi/Yamazaki Sousuke
Kudos: 9





	Advantages

**Author's Note:**

> Do you ever write like 4k of smut whilst sat with your family...no? just me? okay  
> This isn't even what I was intending to write but I felt like this should be sort of an introduction sort of? But who knows when I'll get around to writing my original idea haha

Having two alphas could be argued to be both a good and a bad thing. Kisumi had learnt this first hand quickly after reconnecting with Sousuke and Rin.

Although he hadn't been intending to find a mate or two for that matter, one thing had lead to another and soon enough he found himself wearing matching bite marks on his neck from the two alphas.

He had already settled on a long list of advantages that came with having two mates, from the extra protection he got from creeps anytime they went out to his heats lasting half as long due to the constant fucking rather than the usual cycle of fucking and resting. 

Summer was in full swing and Samezuka's cultural festival came around and although Kisumi had originally thought he would be unable to attend, his heat deciding not to arrive the previous day lead him to his current situation, walking through the Samezuka grounds in search of Rin and Sousuke who seemed to choose the best times to completely disappear.

Even after he eventually spotted Sousuke, he found himself baffled by the alphas strange behaviour, wondering if there was some memo about today he didn't receive.

Just as he was about to ask, he noticed Sousuke's eyes widen and before and felt strong arms wrap around him, pulling him around the corner with a hand clamped on his mouth.

Okay, now he was really confused. And a little turned on if he was honest.

Regardless, he still didn't have a clue what was going on as Sousuke kept his grip on him whilst simultaneously leaning around the corner, hand clutching a...water gun?

"Sousuke? What are yo-"

"Shh,"

He complied, if only because he heard another voice, low and threatening and...strangely familiar? His brain scrambled trying to decode what on earth was going on.

His answer, as to whose voice that was, came in the form of water splashing in his face, dripping uncomfortably down his uniform as he squinted his eyes open against the dripping water from his hair.

"Kisumi?" Makoto stood before him, clearly as confused as Kisumi who turned just in time to see Sousuke around the corner out of sight, calling out a quick

"Sorry Kisumi, I'll explain later,"

With that, Makoto took off after him, Leaving Kisumi with his head spinning in confusion.

_What on earth?_

After taking a minute to compose himself as best as he could, Kisumi continued his search, figuring that maybe Rin would have some sort of explanation as to what was going on. He better had, Kisumi was beginning to get cranky.

Apparently whatever was going on, Rin was in on too as he startled at the feeling of Kisumi's hand on his shoulder, spinning around to reveal he was also brandishing a water gun.

This time, Kisumi at least had the chance to greet his boyfriend however, he still received no explanation as Rin spotted Haru preparing to shoot, ducking out of the way and leaving Kisumi to get hit by a stream of water for the second time that day.

Kisumi pouted at Haru's frankly pathetic excuse, noticing that his other boyfriend had set off running away just as Sousuke had.

"Sorry, Kisumi! We'll catch up with you later,"

Kisumi let out a small huff, a pout taking up residence on his face as he decided to take a quick look round until everyone had finished...whatever it was they were actually doing. Maybe when they'd finished they would actually explain.

He ended up getting his explanation in the form of Makoto calling out to him as he wandered around.

"Sorry about before Kisumi," Makoto rubbed the back of his neck nervously "I didn't expect Sousuke to play so dirty,"

Kisumi couldn't help the laugh that escaped him "Believe me you should start expecting it, have you never wondered how he wins practically every bet?"

Makoto hummed, giving an explanation of what was happening as they followed after the only remaining players.

Haru and Sousuke stood back to back, on the lookout for Rin who was seemingly nowhere in sight, however, he must have been somewhere nearby though as Kisumi could smell his scent rather strongly.

When he stopped to think about it, he realised that it wasn't only Rin's scent that was stronger than usual, Sousuke's was also helping to drown out any background scents.

Well shit. That was _never_ a good sign.

Kisumi could feel the swirling of panic in his stomach mixing with a burning heat that began spreading through his limbs as he realised what was going on, eyes flicking between Sousuke who was now sprawled across the grass and Rin who was standing opposite Haru, each with their gun raised.

_Of course_ his heat would choose the most inconvenient time to start. He should have known, he should have just stayed home, he should have-

"Oi, Kisumi," Rin's voice interrupted his train of thought although he couldn't focus on what the redhead was saying. The only response he could give was a pathetic whine fuelled by self-pity and loathing and _desperation_.

Sousuke, having heard Kisumi's whine realised what was going on, leaning down to wrap an arm around Kisumi's waist to hoist him up onto his good shoulder. Kisumi whined in embarrassment at the situation, kicking his legs pathetically as Sousuke began walking away from the group in the direction of the dorms.

"Ah, We'll see you guys later," Rin was left to excuse them from the group, hoping that everyone would get what he was hinting at as he jogged to catch up to Sousuke.

Kisumi was wriggling in his hold and Rin couldn't help but grin, reaching to ruffle Kisumi's hair with a laugh.

"Kisumi, relax. We'll help you through it,"

"It's embarrassing.." It was mumbled into Sousuke's shoulder but they both made it out easily enough.

"Would you rather go into heat in front of everyone?" Sousuke asked his voice a low rumble that made Kisumi melt. Another whine was the response he got and so he shifted Kisumi slightly so he could raise one of his hands, aiming a warning swat to the back of Kisumi's thighs.

"Sousuke..." Another whine, this one causing Rin to let out a laugh.

"You know he's trying to rile you up, right?" The redhead poked Sousuke in the ribs

"Oh I know," Kisumi shuddered at the tone of Sousuke's voice "Believe me I'll get my own back,"

"Ooo scary," Rin teased, leaning up so that he could whisper in Kisumi's ear "I don't know if Sousuke's the one you should be scared of though," He quickly nipped Kisumi's ear with sharp teeth as they paused outside their dorm before searching his pockets for his key.

When Sousuke dropped Kisumi onto the bottom bunk, both alphas took in a sharp breath at the sight. His face was flushed a shade darker than his hair, travelling down his neck underneath his still wet uniform. Amythyst eyes were glazed over with want as he stared up at the two alphas, clearly much further gone than either of them had anticipated.

"Hnngh," Kisumi whined again, shifting around with the hope that one of them would just do something and it seemed to work, snapping them out of whatever trance-like state they were in previously.

Rin shifted to sit behind Kisumi, the omega propped up against his chest as he attacked his neck with sharp nips and bites whilst Sousuke made quick work of pulling Kisumi's clothes off.

As soon as Kisumi's chest was exposed, Sousuke immediately latched onto a nipple, teeth closing around the hardened nub drawing a high pitched moan from Kisumi who arched off the bed as much as he could with Rin holding him in place.

"Your heat's late," Sousuke spoke with his mouth mere millimetres away from Kisumi's nipple, blowing hot air onto the wet skin making him writhe beneath him.

"Hm...Yeah..." Kisumi had his head tilted to the side as Rin sucked another mark just above one of the mating bites on his neck.

"You didn't know it was going to start today right?" Rin added, his voice laced with danger, urging Kisumi to answer carefully. He took a moment to think past his arousal, opening his mouth to respond only to be beaten to it by Rin "You should know how dangerous it can be Kisumi,"

"I didn't know," He admitted, shuffling impatiently seeing as both his mates had stopped what they were doing "I would've called...or texted...but...hnng...can one of you please just do something,"

After exchanging a look, the two alphas resumed their previous positions, with Sousuke now moving lower to pull Kisumi's pants down and throw them across the room, leaving him vulnerable to their hungry gazes. Rin took this opportunity to grip Kisumi's chin, tilting his head round to slam their lips together in a kiss that was more teeth than anything else.

He couldn't help but moan into Rin's mouth as Sousuke began attacking his thighs with bites, although he didn't have Rin's unusually sharp teeth, Kisumi's thighs were a lot more sensitive than his neck, leaving him squirming. His dick had long since hardened and it lay pathetically on his lower stomach, neglected as his alphas focused more on marking him as theirs.

Rin had broken apart from his mouth, moving to lick and suck at the scent gland on one side of Kisumi's neck, filling the room with the scent of omega, clearly aiming to drive himself and Sousuke crazy. Kisumi could see the way Sousuke's eyes dilated and he imagined Rin's would be much the same, however, his thoughts were cut off by a particularly hard bite to his inner thigh, signalling Sousuke's control was beginning to snap.

"You smell so good," Rin's chest rumbled against his back as he spoke and Kisumi practically purred, something deep within him telling him that this was good, that he was surrounded by his mates.

And oh how good it was.

After sending some sort of telepathic message to Sousuke through the slightest eye contact, Rin shifted Kisumi so that he was on all fours, kneeling in front of him whilst Sousuke moved behind him, hands gripping his hips in a way that made Kisumi keen.

It wasn't the first time they had been in this situation and Kisumi was certain it wouldn't be the last. If his past encounters with his mates during his heat were anything to go off, he had a vague idea of what would happen. More often than not, Rin would tease him until he was close to tears which Kisumi loved at times, however, towards the start of his heat he was too wound up in anticipation that it was a struggle to get him adequately prepared let alone anything else.

Sousuke was currently being reminded of how difficult it was to deal with a desperate Kisumi as he slipped two fingers in, having to drape himself across Kisumi's back with his free arm wrapped around his waist to keep him still. Rin didn't seem to be having anywhere near as much trouble with the now desperate omega who had his lips wrapped lazily around Rin's tip, sucking and licking messily with closed eyes.

"Stay still," Sousuke growled low next to Kisumi's ear, quickly nipping the skin before returning to his previous position, releasing his grip on Kisumi to instead watch how his fingers disappeared inside him. It was entrancing to watch, especially as he added a third finger with ease, spreading them apart with a growl of appreciation. Kisumi's thighs were trembling, the tops of them covered in his slick which Sousuke was fighting himself not to lick off.

A groan from Rin dragged his attention away from Kisumi who had begun rocking into Sousuke's movements, the action also allowing Kisumi to bob his head slowly, arms struggling to support him. Kisumi pulled away with a pop, something slurred and desperate slipping from his mouth that Sousuke managed to make out as something along the lines of 'fuck me'.

"Okay, okay. We've got you," Rin stroked a hand through Kisumi's hair, pushing it away from his face to reveal clouded, lust-filled eyes. Sousuke took this moment whilst Kisumi was distracted to push in, bracing himself as Kisumi let out a seemingly inhuman whine.

The room was filled with nothing but heavy breathing for a moment as Sousuke stilled to allow Kisumi to adjust. Rin fought the urge to push further into Kisumi's mouth until Kisumi began wriggling between them, urging them to just _move_.

His wish was granted as Sousuke pulled back, painfully slow before slamming in, setting a rough pace from the start.

The movement pushed Kisumi's entire body forward and he found his throat constricting around Rin's dick, the redhead moaning, hands grabbing Kisumi's shoulders to help him regain his balance. Aborted pleads escaped Kisumi's mouth every time he pulled back from Rin's dick, only to be cut off with Sousuke's next thrust. Rin pulled back slightly, making it so that even as Sousuke thrust in, Kisumi didn't sink down fully on his dick. After all, his intention at the moment wasn't to get himself off, it was purely to keep himself on edge until Sousuke had fucked Kisumi through the first wave of his heat. Once the first painfully intense wave was done, Kisumi could usually deal with Rin's teasing. That was usually where the fun started.

A well-aimed thrust hit Kisumi's prostate head-on and his arms almost collapsed beneath him at the shocks of pleasure shooting through his limbs. A garbled moan escaped around the tip of Rin's dick and Sousuke took this as encouragement, aiming his thrusts to the same spot and making Kisumi see stars. 

He was close and found himself trying to let Sousuke know with helpless moans, letting himself be dragged this way and that like a ragdoll until he finally, _finally_ felt Sousuke's hips begin to stutter and his knot beginning to catch on Kisumi's rim. The moan Kisumi let out was impossibly loud and Sousuke quickly realised that Kisumi had come without even being touched, the thought of which made his knot finally lock in place.

Rin took his cue to move to the side, allowing Sousuke to pull Kisumi to lie down, the redhead taking his place in front of Kisumi, reaching up to stroke his face gently as purple eyes flickered open.

"Hey," Rin spoke softly, somehow completely ignoring his erection pressing against Kisumi's thigh "How are you feeling?"

"Hmm," Kisumi squirmed slightly in Sousuke's hold, the feeling of his knot shifting igniting a flame of arousal once more albeit somewhat less desperate than before. "A bit better. Probably not for long though," 

Knowing how fast the next wave of a heat can approach, Rin moved to grab a bottle of water off the bedside table, placing it on the bed before helping to manoeuvre Kisumi so that he could sit up without pulling uncomfortably on Sousuke's knot. He gulped down as much water as he could before flopping back against Sousuke's chest with a sigh.

"I'm tired already," Kisumi sighed, always quick to feel the draining effects of heats.

"It'll be over before you know it," Sousuke's voice rumbled behind him.

He was right and Kisumi knew it. Most people would deal with a wave at a time, having a quick nap between to ward off the next wave for a while, however, having two alpha's meant Kisumi could deal with each wave one after another without a break. Although it left him more drained afterwards, it also meant that he wouldn't be waking up burning hot and desperate to be knotted which he found he hated with a passion.

With his thoughts wandering, he found himself hyper-aware of the feeling of Sosuuke's knot slowly deflating, his release burning inside him as Kisumi felt his dick twitch in excitement once more.

He couldn't hold back the quiet whine that escaped him as he felt Sousuke slip out of him, Rin immediately pushing him onto his back and moving to straddle him.

"Ready to go again?" the redhead asked, hovering dangerously close, ready to pounce as soon as he got the go-ahead.

"Rin, please," Kisumi groaned, trying to lift his hips to brush against Rin.

Hands gripped his hips, stopping him from moving and after a quick kiss, Rin moved down so that he could wrap his mouth around Kisumi's dick, sucking hard and ripping an almost scream from Kisumi.

Slipping more of Kisumi's length into his mouth, Rin let out a groan, the vibrations sending jolts of pleasure through kisumi's needy body as he wriggled and struggled to move in Rin's hold.

The feeling of slick as Sousuke's release dripped down onto the sheets below him, whilst not pleasant, send a rush of animalistic desire through him and Kisumi wanted nothing more than for Rin to fuck him, and fast.

It seemed however that Rin has other plans as he dragged his tongue up the side of Kisumi's dick, sucking and mouthing at the head before sinking back down, his sharp teeth held a safe distance away (Something that had unfortunately been learnt through trial and error).

"Rin...Please..." Kisumi felt tears of frustration welling up in his eyes which were quickly wiped away by Sousuke's warm hands.

"You're gonna feel so good," Sousuke's hushed voice sent shivers down Kisumi's spine which, when mixed with Rin's throat constricting around him, made him jerk, desperation flooding over him in waves as he reached the brink of release.

Much to his relief, Rin didn't seem to be in the mood to deny him, sucking and swallowing around him until he screamed loud enough to disturb the rest of the dorm. The redhead held his hips down as he released, swallowing quickly around him until Kisumi was twitching and moaning at the sensitivity that had lit every nerve in his body alight.

"Hnng...No more...Rin," Kisumi tried to reach down to tangle his fingers in Rin's hair with the intention of pulling him away, however, his arm was caught before he could even realise what was happening. With his arm now pinned by Rin, with the other likely to share the same fate if he tried again, he could only shudder as Rin continued to suck hard, taking full advantage of Kisumi's helplessness.

The feeling of one of Rin's fingers entering him was enough to temporarily snap Kisumi out of his hazed state, managing to focus just enough to see him pull away, replacing his hand with his mouth.

"Is this alright?"

He could only groan in response, his body reacting despite its sensitivity.

_Oh, how he hated heats._

He could barely even feel his limbs when Rin pushed in, his head feeling like it was full of cotton wool, only able to focus on the feeling of Rin hitting his prostate with each thrust.

He was sure he must have blacked out at some point because the next thing he remembered was being curled into Rin's chest with his knot buried deep. Fingers tangled in his hair, pushing it away from his face, setting off a rumbling purr in his chest that Rin couldn't help to grin at.

"You're awake," He stated, sounding relieved. "Are you alright? Is it still bad?" The door opened whilst Rin was talking and Sousuke's voice quickly joined in

"I doubt he wants to play 20 questions after just waking up," Kisumi felt the bed dip behind him, lazily tilting his head to see Sousuke placing a plate of food down on the bedside table. "You should eat something before it starts up again,"

Another whine as he flopped his head back down dramatically pawing at Sousuke's arm in an attempt to drag him to lie down with them.

"No more..." He knew he was being childish and that neither of them could stop his heat midway through, however, he was tired and sore and just wanted it to be over already.

"We could always take a break. You could get some sleep to hold off the next wave," Rin suggested. Whilst Kisumi realistically knew that, he also knew that it would be easier to continue now whilst he was still somewhat sated from the previous rounds.

Rin's knot began deflating and the two of them helped Kisumi to sit up enough to eat after Rin had slipped out.

"I want you both to fuck me," Kisumi spoke after some time, catching the two alphas off guard. "At the same time," 

After exchanging a glance with Rin, Sousuke joined them on the bed.

"We can do that. We've done it before," Rin assured, fingers playing with the hair at the base of Kisumi's neck

"No...I meant...I want both of you in my ass..." Kisumi's face was flushed once more, whether it was down to his request or the final parts of his heat they didn't know.

"Are you sure?" Sousuke asked, face set with concern. Kisumi only nodded, deciding to take control, of the situation. 

He pushed Rin down onto the bed, figuring he would make the redhead's life easier after fucking him through the last wave. His knees buckled as he sank down quickly, moaning as he slumped forwards against Rin's chest. He knew that he was being needy, demanding, all the things that people didn't want in an omega but he still felt uncomfortably hot and needy and he just wanted to be filled. 

He reached behind himself with one hand, the other being used to support himself as he slipped a finger in alongside Rin's dick, moaning and mumbling nonsense as he tried to reach his release once more.

He could tell this was the last of it, however, with his body being so sensitive and abused it made it so much harder to reach that high. He slipped in another finger, barely feeling the stretch from being knotted multiple times, however, a hand wrapping around his wrist ripped a desperate whine from his throat as he tried to pull his arm away.

"Sousuke...Let go!" Kisumi was close to tears with how desperate he felt, fighting against the alpha who let out a warning growl.

"Kisumi," He shrunk at the sound of it, no longer fighting the alpha who had now pressed himself against Kisumi's back, pinning his arm behind him as he reached down and pressed into Kisumi with his own fingers, all the while nipping sharply at Kisumi's neck.

"Damn Kisumi, trying to fight against Sousuke. I've even seen some alphas back away from that," Rin laughed breathlessly from beneath him. Another whine was the only response he got as he reached up to play with Kisumi's nipples, not able to do much more in his current position.

The pressure around his dick grew with each finger that Sousuke slipped in and Rin couldn't help wriggling at the feeling.

With each finger that was added, Kisumi whined, desperate tears slipping from his eyes until finally, he felt Sousuke's fingers retreat, being replaced by the head of his dick prodding gently, not quite entering yet. Instead, he released his hold on Kisumi, returning him to his original position against Rin's chest before finally pressing in, painfully slowly as his hands pressed bruises into Kisumi's hips.

"Fuck....Hnng..." Kisumi sobbed at the feeling, at the impossible stretch as Sousuke began a rough pace, slamming in all the way each time.

Rin didn't quite know how he managed to stay in place, putting it down to Kisumi's limp body sprawled across him, pinning him to the bed. His arms wrapped tightly around Kisumi's waist as he leaned up for a messy kiss and he almost cringed at the wet sounds filling the room with every thrust.

It was almost painful with how sensitive he was but Kisumi relished in it, too far gone to even consider how much of a pain any sort of movement would be after this. He was only brought back to the current situation as he heard Sousuke grunt above him, eyes flicking open to see Rin wasn't doing much better.

"Kisumi, we can't both knot you without hurting you," He cried out in response but Sousuke was still aware enough to know not to even consider it.

"Please..." Kisumi was willing to beg at this point, he could feel both his alphas knots swelling, brushing against each other and pushing against him and he wanted nothing more than to be filled by them.

Ignoring Kisumi's pleading, Sousuke locked eyes with Rin over Kisumi's shoulder, his question coming out as a grunt "Are you close?"

Rin nodded, groaning as Sousuke pulled Kisumi back up against his chest, urging him to bounce on Rin's cock as Sousuke himself slipped out.

Of course, Kisumi protested, hands grabbing onto any part of Sousuke he could, only for Sousuke to grab his wrists again in one hand, the other reaching around Kisumi to pump his dick.

With synchronised groans, Rin and Kisumi came together, the omega slumping bonelessly against Rin as Sousuke quickly finished himself off, streaks landing across Kisumi's back only to be smeared seconds later by Sousuke pressing himself againt Kisumi.

They stayed that way for a few moments, catching their breath until Rin let out a wheeze from beneath them.

"Okay, I love you but damn you're both heavy," The redhead complained, grunting in relief when Sousuke rolled to the side with a laugh.

Kisumi didn't have much choice but to stay where he was with Rin's knot buried deep inside him, not that he would move if they weren't currently joined together seeing as he was on the brink of passing out.

"Get some sleep Kisumi," Sousuke gently flicked his forehead, knowing that Kisumi was trying everything in his power to stay awake with them. 

The pout he was given was fully expected however, he brushed it off, shuffling out of bed to grab a warm washcloth to wipe Kisumi down. After all, it didn't look like he would be moving anywhere anytime soon, not that he and Rin were in much of a better condition.

When he returned, Kisumi was fast asleep, curled as much as possible with his current position and Rin had allowed his eyes to slip closed, only briefly opening them to glance at Sousuke as he reentered. He made quick work of cleaning his own release off Kisumi's back, throwing the washcloth off to the side as he let his hands travel over Kisumi's smooth skin, gently kneading the muscles there and feeling as the tension flooded from Kisumi's back.

"So much for your big scary alpha image," Rin snorted from beneath Kisumi, trying not to jostle the omega around too much as he watched Sousuke's hands work.

"You were the one that started that joke in the first place," Sousuke retorted, laughing at the grumble Rin let out.

"Asshole," Kisumi let out a whine in his sleep and Rin reached up to stroke his hair gently "Hurry up and come sleep. Kisumi said so,"

"Kisumi's asleep, he didn't say shit," Sousuke contemplated throwing the washcloth from before in Rin's face but decided against it upon realising that Rin staying still was the key to not waking Kisumi. "Give me a second,"

After quickly grabbing their discarded clothes and the discarded washcloth to throw in the laundry, he finally joined his boyfriends, sitting up against the headboard, letting his hand drift down to trace patterns onto Kisumi's shoulders.

"You should sleep too, not like you can do much else," Sousuke turned to Rin, only to find the redhead's eyes already closed, breathing even and soft, forcing a fond smile onto Sousuke's face.

He may have lost the water gun fight but this was by far better. Watching his boyfriends content made up for the fact that one of the previously mentioned boyfriends had been the one to beat him earlier.

Or at least, it was better right now, whilst the two were asleep. No doubt when Kisumi woke up there would be hell to pay for how sore he would no doubt be.

That, however, sounded like a problem for future Sousuke to deal with.


End file.
